In some inkjet printer ink cartridges the ink is held inside the cartridge in a foam ink holding material. Although the foam usually occupies substantially all of an ink holding chamber inside the cartridge, small voids or pockets around the foam may exist, particularly along the bottom and in corners of the ink holding chamber. Also, it may be desirable in some cartridges to only partially fill an ink holding chamber with foam, for example to vary the amount of ink held in the cartridge without also changing the size or shape of the ink holding chamber, thus leaving areas of the ink holding chamber unoccupied by foam. A foam filled ink holding chamber is usually vented to the atmosphere through the lid of the cartridge. Air may become trapped in voids or pockets around the foam or in other areas of the ink holding chamber not occupied by foam if those areas are sealed off from the lid vents. Improper venting in these areas may inhibit the ability of the foam to absorb (or re-absorb) ink that may collect in these areas or otherwise adversely affect performance of the cartridge.